This invention pertains to a multiple thermocouple system used for frequently monitoring the temperatures of a metal vessel wall. It pertains particularly to a thermocouple system in which a first conductor wire is attached to a vessel wall and the vessel wall provides a portion of the second conductor of the thermocouple, and both conductors are connected to switching means and to a voltmeter.
With the advent of digital computers that are relatively cheap, it is now possible to monitor much greater amounts of data automatically than was previously possible for information purposes and also for safety purposes. A common problem for which this capability would be of great value is monitoring high pressure, high temperature reactors in which local overheating of the wall can lead to failure and must be prevented. Heretofore, it has been very expensive to install and monitor thermocouples, with costs being approximately $1,500 per thermocouple. However, with the advent of modern data acquisition systems using digital computers, it is possible to scan and monitor very large numbers of thermocouples very economically, particularly if all that is required is to activate an alarm if the temperature rises above a given value.
Multiple thermocouple systems for the rapid measurement of temperatures such as in reactors have been developed previously. For example, U.S. Pat. No. 3,459,925 to Goosey, et al discloses a system for rapidly scanning a large number of conventional type dual conductor thermocouples. Also, U.S. Pat. No. 4,008,049 to Clemmer, et al discloses apparatus for measuring peak temperatures within a tubular type reactor, also using conventional dual conductor type thermocouples. However, because these temperature monitoring systems utilize conventional dual conductor thermocouples, their cost per thermocouple are undesirably greater than that for the thermocouple system of the present invention.